1. Submillimeter water megamasers in nearby AGNs
Dom Pesce
Presentation for SES APS conference
November 12, 2016

2. 22 GHz megamasers • What they can’t tell us • Submillimeter megamasers
22 GHz water megamasers
22 GHz megamasers • What they can’t tell us • Submillimeter megamasers

3. 22 GHz megamasers • What they can’t tell us • Submillimeter megamasers
22 GHz water megamasers
What are they?
22 GHz megamasers • What they can’t tell us • Submillimeter megamasers

4. 22 GHz megamasers • What they can’t tell us • Submillimeter megamasers
22 GHz water megamasers
What are they?
The water molecule has a rotational transition with a rest frequency of 22 GHz (radio regime)
22 GHz megamasers • What they can’t tell us • Submillimeter megamasers

5. 22 GHz megamasers • What they can’t tell us • Submillimeter megamasers
22 GHz water megamasers
What are they?
The water molecule has a rotational transition with a rest frequency of 22 GHz (radio regime)
Under certain physical conditions, the water molecules can experience a population inversion, leading to maser activity
22 GHz megamasers • What they can’t tell us • Submillimeter megamasers

6. 22 GHz megamasers • What they can’t tell us • Submillimeter megamasers
22 GHz water megamasers
What are they?
The water molecule has a rotational transition with a rest frequency of 22 GHz (radio regime)
Under certain physical conditions, the water molecules can experience a population inversion, leading to maser activity
22 GHz megamasers • What they can’t tell us • Submillimeter megamasers

7. 22 GHz megamasers • What they can’t tell us • Submillimeter megamasers
22 GHz water megamasers
Where are they?
22 GHz megamasers • What they can’t tell us • Submillimeter megamasers

8. 22 GHz megamasers • What they can’t tell us • Submillimeter megamasers
22 GHz water megamasers
Where are they?
Observed in thin, edge-on accretion disks around supermassive black holes (SMBHs) in active galactic nuclei (AGNs)
NGC 5765b
22 GHz megamasers • What they can’t tell us • Submillimeter megamasers

9. 22 GHz megamasers • What they can’t tell us • Submillimeter megamasers
22 GHz water megamasers
Why do we care?
NGC 5765b
22 GHz megamasers • What they can’t tell us • Submillimeter megamasers

10. 22 GHz megamasers • What they can’t tell us • Submillimeter megamasers
22 GHz water megamasers
Why do we care?
They provide the only means of directly mapping molecular gas in AGNs on sub-parsec scales
NGC 5765b
22 GHz megamasers • What they can’t tell us • Submillimeter megamasers

11. 22 GHz megamasers • What they can’t tell us • Submillimeter megamasers
22 GHz water megamasers
Why do we care?
They provide the only means of directly mapping molecular gas in AGNs on sub-parsec scales
They act as test masses inside the SMBH’s sphere of influence, allowing us to kinematically measure the mass of the black hole
22 GHz megamasers • What they can’t tell us • Submillimeter megamasers

12. 22 GHz megamasers • What they can’t tell us • Submillimeter megamasers
22 GHz water megamasers
Why do we care?
They provide the only means of directly mapping molecular gas in AGNs on sub-parsec scales
They act as test masses inside the SMBH’s sphere of influence, allowing us to kinematically measure the mass of the black hole
Their geometry is such that we can use them to make distance measurements to the host galaxy
22 GHz megamasers • What they can’t tell us • Submillimeter megamasers

13. What 22 GHz masers can’t tell us
22 GHz megamasers • What they can’t tell us • Submillimeter megamasers

14. What 22 GHz masers can’t tell us
The 22 GHz masers are excellent dynamical probes of the accretion disk
But they can’t tell us much about the physical conditions
Gas temperature
Gas density
Dust temperature
22 GHz megamasers • What they can’t tell us • Submillimeter megamasers

15. Submillimeter water megamasers can help do what 22 GHz alone cannot
22 GHz megamasers • What they can’t tell us • Submillimeter megamasers

16. Submillimeter water megamasers can help do what 22 GHz alone cannot
The water molecule has a complex structure of rotational energy levels
para
ortho
22 GHz megamasers • What they can’t tell us • Submillimeter megamasers

17. Submillimeter water megamasers can help do what 22 GHz alone cannot
The water molecule has a complex structure of rotational energy levels
para
ortho
22 GHz megamasers • What they can’t tell us • Submillimeter megamasers

18. Submillimeter water megamasers can help do what 22 GHz alone cannot
The water molecule has a complex structure of rotational energy levels
Several of these transitions can generate maser emission in the sub-mm wavelength range accessible with ALMA
22 GHz megamasers • What they can’t tell us • Submillimeter megamasers

19. Submillimeter water megamasers can help do what 22 GHz alone cannot
The water molecule has a complex structure of rotational energy levels
Several of these transitions can generate maser emission in the sub-mm wavelength range accessible with ALMA
Combining observations of multiple transitions will allows us to constrain the physical conditions in the accretion disk as a function of radius
22 GHz megamasers • What they can’t tell us • Submillimeter megamasers

20. Submillimeter water megamasers can help do what 22 GHz alone cannot
Circinus
22 GHz
321 GHz
22 GHz megamasers • What they can’t tell us • Submillimeter megamasers

21. Submillimeter water megamasers can help do what 22 GHz alone cannot
NGC 4945
22 GHz
321 GHz
22 GHz megamasers • What they can’t tell us • Submillimeter megamasers

22. 22 GHz megamasers • What they can’t tell us • Submillimeter megamasers
Conclusions
22 GHz water megamasers have proven to be useful tools for measuring SMBH masses, distances to galaxies, and H0
ALMA has now opened up the possibility of studying sub-mm megamasers
Observations of multiple masing transitions in a single system will constrain the physical conditions in the accretion disk
Several systems have already been observed to host sub-mm megamasers
The ultimate goal is to be able to map out the radial temperature and density profiles of these accretion disks
Upcoming work will focus on spatially resolving the sub-mm maser distribution
ALMA can do this for the closest systems
More distant targets will require (sub)mm-VLBI
22 GHz megamasers • What they can’t tell us • Submillimeter megamasers

23. References Braatz, J. A., et al. 2010, ApJ, 718, 657
Gao, F. et al , ApJ, 817, 128
Gray, M. D. et al , MNRAS, 456, 374
Hagiwara, Y. et al , ApJL, 768, L38
Humphreys, E. M. L. et al , A&A, 592, L13
Lo, K. Y , ARAA, 43, 625
Pesce, D. W., Braatz, J. A., & Impellizzeri, C. M. V , ApJ, 827, 68
Reid, M. J. et al , ApJ, 767, 154
• References •